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If materials science has a "character", then Titanium is definitely a tsundere.

It's light, strong, and corrosion-resistant, all seeming advantages.
But if you asked any mechanical engineer in the 1950s: "Would you want to make something out of titanium?"
He will most likely throw the wrench in your face and walk away cursing.

Because this thing is too high maintenance. It is as hard as stone, as sticky as chewing gum, and the purest mineral vein on this earth is in the hands of the Soviet Union.

But Americans can't help it. In order to create that monster called the SR-71 "Blackbird", they had to kneel down and chew off the hard bone of titanium.


1. A plane that “pees its pants” on the runway

Let me start with some trivia: the SR-71 "Blackbird", the fastest and highest mass-produced reconnaissance aircraft in human history, is an oil leaker on the ground.

When it is parked on the runway, aviation fuel will drip from the bottom of the fuselage, and ground crews must be ready to clean it up at all times, otherwise a cigarette butt can burn this treasure worth hundreds of millions of dollars.

Is it because the processing accuracy of Americans is not enough?
No, this is intentional.

Because this plane has to fly to Mach 3.2 (more than 3 times the speed of sound). At this speed, the air is no longer a gentle wind, but sandpaper and flames.
The temperature on the surface of the fuselage will soar to 300℃-500℃.

At this temperature, ordinary aluminum alloys (the material used to make Coke cans and Boeing airliners) have long since become as soft as mud;
Use stainless steel? It's too heavy and the plane can't fly high at all.

This forces engineers to choose titanium alloy. 93% of the entire SR-71 aircraft is made of titanium alloy.

But this brings about a physical problem: thermal expansion and cold contraction.
Titanium alloys expand when heated. Engineers calculated that when an airplane is racing at an altitude of 30,000 meters and becomes red, the length of the fuselage will stretch several inches.
If the fuel tank is sealed tightly on the ground, in the sky, the expanding fuselage will directly tear the fuel tank apart.

Therefore, engineers can only leave gaps in the ground.
This led to that embarrassing scene: This aircraft, the crown jewel of human industry, was leaking oil like an old man who couldn't hold his urine before taking off.
Only when it soars into the sky, friction generates heat, the fuselage expands, and the gaps close, does it turn back into that perfect black ghost.

2. CIA’s “overseas purchasing” operation

Now that we have decided to use titanium, the next question is: Where does titanium come from?

In the 1950s, titanium was not only expensive, but also scarce.
What's even more terrible is that at that time, the highest quality rutile (ore for refining titanium) origins in the world were all in the Soviet Union. **

This is very embarrassing.
The Americans wanted to build a reconnaissance aircraft that could fly over the Soviet Union to take pictures, but the materials to build the aircraft had to be purchased from the Soviets.
If the Soviets knew the truth, they would probably laugh out loud in the Kremlin and immediately cut off the confession.

As a result, the CIA (U.S. Central Intelligence Agency) was forced to change careers and became a "traitor."
They set up a bunch of shell companies, pretended to be civilian traders, and moved around the world.
"Hey, Davari, we need to buy some titanium for pizza ovens/golf clubs/chemical pipes..."

The Soviets looked at the colorful dollars and thought that they were only used for civilian industry and it would be good to earn some foreign exchange, so they sold them.

In this way, ship after ship of titanium ore swaggered across the Iron Curtain and was transported to Lockheed's "Skunk Works" in the United States.
The Soviets themselves provided the Americans with the sword that pierced their airspace. This is probably the biggest black humor in the history of the Cold War.

3. Engineer’s nightmare: This thing has “germophobia”

Scamming the ore is just the beginning, processing titanium alloy is the real hell.

Titanium, a metal, has an extremely abnormal "chemical affinity".
In high temperatures, it is like a sea king, flirting with everyone it meets. Oxygen, nitrogen, and hydrogen all have to react. Once it reacts, it becomes brittle and crumbles when lightly tapped.

In order to serve this man, American engineers are going crazy.

  • All welding must be performed in an expensive sealed chamber filled with inert gas (argon).

  • All drill bits are useless after they can't drill a few holes, because titanium is too hard and sticky, and the bit will be worn away.

  • The most outrageous thing is water. One summer, inexplicable cracks suddenly began to appear in the titanium alloy welds in the factory. After checking for several months, I finally found out that it was a problem with the tap water.

    • The city of Burbank's water plant adds a little more chlorine to the water in order to disinfect it.
    This trace amount of chlorine washes onto the parts, causing the titanium alloy to embrittle.
    There is no other way, the factory can only spend a lot of money to buy distilled water to clean the parts. A fighter jet has to use distilled water for bathing. No one else has this kind of treatment.

    4. A murder caused by a screw: Cadmium Embrittlement

    During the assembly process, a strange thing happened.
    The inspector found that many titanium alloy bolts had the right torque, but their heads fell off after a few days.

    This is simply a supernatural event.

    After a thorough investigation, the murderer turned out to be the worker's wrench.
    According to the practice in the aviation industry, in order to prevent rust, the surface of many tools (wrenches, pliers) will be plated with a layer of Cadmium.
    Cadmium is a very common metal that prevents rust.

    However, when a cadmium-coated wrench comes into contact with a titanium bolt, trace amounts of cadmium atoms are left behind.
    It's fine at room temperature. But don't forget, this plane has to fly to 500 degrees Celsius.
    At this temperature, cadmium will penetrate into the grain boundaries of titanium atoms just like mercury penetrates into sand, directly cutting off the metal bonds of titanium.
    This is called "liquid metal embrittlement".

    Just because the plating on the wrench is touched, a bolt that costs thousands of dollars will be useless.
    In the end, Lockheed had to throw all the cadmium-plated tools in the factory into the garbage and replace them with special cadmium-free tools. It also strictly inspected the workers' tool boxes and fired anyone who dared to bring in cadmium-plated items.

    5. Ending: Expensive Loneliness

    In 1998, the SR-71 "Blackbird" was officially retired.
    It has been flying on this planet for more than 30 years and has never been shot down by any missile.

    Why?
    Because when it detects a SAM missile flying towards it, the pilot only needs to make one action: Push the throttle.
    It accelerated faster than a missile. The missile was chasing behind my butt, ran out of fuel, and fell down.

    This is a victory for materials science.
    It was the titanium alloy skin that was refined from Soviet ores, washed with distilled water, and drove countless engineers crazy. It defeated the laws of physics and made a mockery of that era.


    Conclusion

    Nowadays, titanium alloys are no longer mysterious.
    It's in the frame of your iPhone, in grandma's artificial hip, and in expensive camping water bottles.
    It changed from a "strategic material" to a "lifestyle".

    But every time I touch that cold, warm, gray-sheen metal, I always think of that group of lunatics from half a century ago.

    In order to pursue the ultimate speed, they do not hesitate to deceive the enemy and challenge the limits of the elements.
    The so-called technology sometimes means using the stupidest methods to solve the most difficult problems.
    And material is the hardest stepping stone.